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Series I, Episode 12: Illumination

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Ian Dunn
866983.  Fri Nov 25, 2011 2:22 pm Reply with quote

Here is the preview.

 
suze
867005.  Fri Nov 25, 2011 6:16 pm Reply with quote

Now then, question. I'd heard somewhere before that blindfolded people asked to walk in a straight line tend in fact to walk in a clockwise spiral, but not in such detail as on tonight's show. The research on this was done by one Professor A A Schaeffer in 1928, and Prof Schaeffer also noted that the same happens if a person is asked to swim, row, or (rather scarily) drive a car while blindfold.

Sometimes a person will walk in an anti-clockwise spiral, but clockwise is more common; this is true whether the subject be right handed or left handed.

Prof Schaeffer did his research in Kansas. Had he done it in Australia, would he have found that most people go anti-clockwise?

 
PDR
867008.  Fri Nov 25, 2011 6:49 pm Reply with quote

I don't know why people find this surprising. Given that the mechanics of walking involves repeatedly "falling" in a direction determined by the relative positions of the body centre of gravity and a foot, and that the position of the foot for each pace depends on the hinge properties of the hip and knee plus various geometries of leg, hip etc, any one of which could have an asymetry that would produce a bias to one side, it would be far more remarkable of people DID tend to walk in straight lines without reference to external cues.

PDR

 
Ian Dunn
867025.  Sat Nov 26, 2011 5:58 am Reply with quote

Other than the minor quibble about refering to Red Rum as a person, I thought it was a good show. Interesting to see QI cover Japan again.

 
mckeonj
867039.  Sat Nov 26, 2011 6:38 am Reply with quote

About being blindfold*; I saw on news yesterday David Beckham score a penalty kick while blindfold. Mind you, he is a skilled athlete with enhanced senses of position etc.
I imagine that trained dancers and gymnasts could also work blindfold.

*Not sure about this form.

 
coldalarm
867058.  Sat Nov 26, 2011 8:09 am Reply with quote

I know that this would probably set a klaxon off, but isn't it because one leg is minutely shorter than the other, which would explain the curved motion.

Or maybe just because we all favour one leg over the other?

 
Jenny
867082.  Sat Nov 26, 2011 11:26 am Reply with quote

In that case I would go clockwise, as my right leg is about half an inch shorter than my left, since I broke it when I was a teenager.

 
clack
867091.  Sat Nov 26, 2011 1:36 pm Reply with quote

Chris was knowledgeable and lively, though his jokes were hit-and-miss.

Not a prime performance from Rich. At his best, he makes up for his long stretches of silence with some classic one-liners or bits. Not this time.

I usual find Jack to be a middling guest. Fairly amusing but unmemorable.

My heart sank a bit when Alan got his hands on those invisible water balls, but fortunately the moment passed without getting too tiresome.

I really enjoyed the topics. Another good episode -- series I has been strong so far. Hope it continues to be so.

 
suze
867104.  Sat Nov 26, 2011 5:42 pm Reply with quote

coldalarm wrote:
Or maybe just because we all favour one leg over the other?


We do - and the majority of us are right-legged just as the majority of us are right-handed. It would seem reasonable to suppose that a right-legged person would tend to spiral clockwise, but that would also suggest that a left-legged person would tend to spiral anti-clockwise. Which is not what Prof Shaeffer found - he found that for both right- and left-handed people, clockwise was more common.

Which is why I began to wonder whether it's something to do with the earth's magnetic field. Since physics is not my subject, I didn't develop that idea - but would it indeed suggest that Australians would indeed tend to spiral anti-clockwise?

 
djgordy
867111.  Sat Nov 26, 2011 6:19 pm Reply with quote

On the subtitles it said that the George Best person was killed in a "dual". Well, I suppose there had to be two of them.

 
Posital
867115.  Sat Nov 26, 2011 6:48 pm Reply with quote

But physical impediments and strength should kinda even themselves out over time, as muscles get stronger to compensate.

Anyway - the correction doesn't need to be visual.

Wind direction can give it away - as well as the drone of a motorway in the distance (or the voice of a satnav or echos). Or even the lie of the land - like furrows, a footpath or tightrope.

And even with your eyes closed, you should be able to get a good idea where the sun is.

 
Sylvia
867118.  Sat Nov 26, 2011 6:57 pm Reply with quote

suze wrote:
Prof Schaeffer also noted that the same happens if a person is asked to swim, row, or (rather scarily) drive a car while blindfold.

Surely if you want to drive in a dead straight line, you only have to keep your hands off the steering wheel?

 
djgordy
867120.  Sat Nov 26, 2011 7:02 pm Reply with quote

No because the road has camber* and your car is likely to pull to one side or the other due to unbalanced wheels or some minor defect in the steering mechanism.

Jack Dee's explanation that it is some kind of survival mechanism to return you to the place you left doesn't really make any sense unless there were generations of blindfolded people walking around and only the ones that survived by walking in circles were able to procreate. In the wild though, blind animals (except the ones that live in caves) don't survive long enough to breed and, anyway, they are just as likely to fall off a cliff to the left or right as they are to fall off one straight in front of them.

*I.e. the centre of the road is higher than the sides of the road in order to allow water to drain off.

 
Ian Dunn
867147.  Sun Nov 27, 2011 3:46 am Reply with quote

I found the subject of the fake war footage rather interesting. Sounds like the spirit of Damien Day from Drop the Dead Donkey is alive and well.

 
PDR
867150.  Sun Nov 27, 2011 5:00 am Reply with quote

Sylvia wrote:
suze wrote:
Prof Schaeffer also noted that the same happens if a person is asked to swim, row, or (rather scarily) drive a car while blindfold.

Surely if you want to drive in a dead straight line, you only have to keep your hands off the steering wheel?


Lots of things influence the direction of a car, and even then the "castor" geometry of the suspension on ties it to the local net gravity which (as should be obvious) changes with bumps, turns, slopes etc. Then there are torque-steer issues, crosswinds, variations in traction at the surface and a myriad of other things. That's the "why don't they naturally go straight" part of the question.

The other part is the "why can we not sense and correct the variation" bit, and the same applies to walking and for the same reasons - there is no inherent sense of direction without external cues, so what the body (or car) sense is the *rate* of variation in direction. This means that some function or mechanism is integrating "rate" to get "position" and such integrations are highly susceptable to "zero drift" (noise-induced corruptions of the constant of integration). It's almost impossible to keep the drift manageable without external references, which is why aircraft inertial navigation systems need either something like a GPS or manual input to provide periodic position corrections and null-out the drifts.

PDR

 

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